calculate the empirical formula: 79.8%C and 20.2%H. what os the formula

Take a 100 g sample. That will give you
79.8 g C
20.2 g H.

convert g to mols. mols = g/molar mass.
79.8/12.01 = 6.64
20.2/1 = 20.2

This gives the formula of
C6.64H20.2

However, we know from Dalton's theory that atoms combine in the ratio of small whole numbers. So convert the above values into small whole numbers. Hint: Divide the smaller number by itself; that will make it be 1.000. Then divide the other number by the same value. That is an easy way to convert to small whole numbers.

20.2/20.2 = 1.000

6.64/20.2 = 0.329

So the empirical formula is
C3H20

To convert the values to small whole numbers, divide both numbers by the smaller number, which in this case is 6.64.

6.64/6.64 = 1
20.2/6.64 = 3.04

Round the ratio of carbon (C) to the nearest whole number:

C1

Round the ratio of hydrogen (H) to the nearest whole number:

H3

Therefore, the empirical formula is CH3.

To convert to small whole numbers, divide the smaller number, in this case, 6.64, by itself to make it equal to 1.000. Then divide the other number, 20.2, by the same value.

6.64 / 6.64 = 1.000
20.2 / 6.64 = 3.04

So the empirical formula is:

C1.000H3.04

However, it is generally preferred to express the formula with whole numbers. Since we cannot have a fraction in a chemical formula, we need to multiply the formula by a whole number to get rid of the decimal. In this case, we can multiply the entire formula by 3 to eliminate the decimal in H3.04.

C1.000 × 3 = C3.000
H3.04 × 3 = H9.12

Rounding off, we get:

C3H9

Therefore, the empirical formula is C3H9.